[938] Histological Heterogeneity of Clear Cell Renal Cell Carcinoma (CCRCC). A Complete Morphological Analysis of 47 Tumors

Jose I Lopez, Gorka Muniz, Rosa Guarch, Natalia Camarasa, Maria Caceres, Virginia Moreno, Lola Garcia-Prats, Roberto Orozco. Hospital de Cruces, Univ of the Basque Country (UPV/EHU), Barakaldo, Bizkaia, Spain; Hospital Virgen del Camino, Pamplona, Spain; Hospital Peset, Univ of Valencia, Spain; Hospital General Yagüe, Burgos, Spain; Hospital Txagorritxu, Vitoria-Gasteiz, Spain; Hospital San Jorge, Huesca, Spain; Hospital San Juan de Dios, Ciudad de Guatemala, Guatemala

Background: CCRCC are known to be histologically heterogeneous but no study quantifying this fact in a large group of unselected cases has ever been performed. There is concern that limited kidney tumor sampling protocols in general pathology practice may give a partial and insufficient view of tumor heterogeneity. The aim of this study is to define and quantify the extent of tumor heterogeneity in a series of totally sampled CCRCC.
Design: Sixty-four (64) consecutive renal cell tumors from seven hospitals were totally sampled over a three months period in 2011. 47 (73.5%) of this group were CCRCC. A total of 1439 H&E slides of CCRCC were collected and reviewed applying AJCC staging and Fuhrman nuclear grade. Cases were classified as homogeneous or heterogeneous carcinomas depending on the presence of one or more different cell types and grades in different areas of the same tumor. Basic clinical and pathologic data were retrieved in all cases.
Results: Males predominated in the series (31M/16F), the average age being 62.5 years (range 27-83). Average tumor diameter was 5.9 cm (range 2-19) and average number of paraffin blocks per case was 30.6 (range 3-130). Organ-confined tumors were predominant (59.5%) in the series. Twenty eight CCRCC (59.5%) were histologically heterogeneous with the main histology consisting in Grade 1 and 2 conventional clear and/or eosinophilic cells arranged in nests, cords and pseudoglands. Secondary patterns in these tumors included Grade 3 and 4 areas (17 cases, 60%), sarcomatoid areas (2 cases, 7%), and oncocytoid areas (1 case, 3.5%). Small clear cells (35.7%), necrosis (32.1%), syncytial cells (21.4%), bony metaplasia (14,2%), and papillae (7%) were also focally detected. Homogeneous CCRCC (19 cases, 40.5%) were all entirely composed of conventional Grade 1 and 2 clear/eosinophilic cells. More than one third (36%) of low grade (G1/2) CCRCC had minor high grade (G3/4) areas.
Conclusions: A significant number of CCRCC are composed of different cell types with variable grades that can be incompletely sampled with current protocols. This fact may contribute to the unexpected poor behaviour of some CCRCC. Our data suggest that as many as one third of low grade CCRCC will contain high grade foci if extensively sampled.
Category: Genitourinary (including renal tumors)

Wednesday, March 21, 2012 9:30 AM

Poster Session V # 95, Wednesday Morning


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